High Speed Steel, Cobalt Coated ;Tri-flat shank for sure grip ;Storage in Aluminum Carry Case ;Include Sizes: 1 PC--1/4" Shank--5 Steps: 4mm, 6mm, 8mm, 10mm, 12mm ;1 PC--1/4" Shank--9 Steps: 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm ;1 PC--3/8" Shank--7 Steps: 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm ; 1 PC-5/16" Shank--10 Steps: 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm ; 1 PC--3/8" Shank--15 Steps: 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm, 32mm.